WO2007102602A1

WO2007102602A1 - Mechanical expander and production method for seamless steel pipe

Info

Publication number: WO2007102602A1
Application number: PCT/JP2007/054695
Authority: WO
Inventors: Tsutomu Arita; Masayoshi Akiyama; Kouichi Kuroda; Tatsuya Okui
Original assignee: Sumitomo Metal Industries, Ltd.
Priority date: 2006-03-09
Filing date: 2007-03-09
Publication date: 2007-09-13
Also published as: US7765850B2; EP1992428B1; MX2008011373A; JP2007237257A; CA2644176C; CN101394952A; EP1992428A4; US20090038366A1; JP4983053B2; CN101394952B; EP1992428A1; CA2644176A1

Abstract

[PROBLEMS] To improve the inner diameter size precision of the pipe end portion of a seamless steel pipe to be hot-worked. [MEANS OF SOLVING PORBLEMS] A mechanical expander in which a cone (2) and a die (1) are inserted into a pipe end portion to be pipe-expanded, and the cone (2) is axially drawn toward the outside of the pipe with the die (1) kept fixed at the pipe end portion, whereby the die (1) is radially and outwardly spread out by a wedge action to pipe-expand the pipe end portion. A taper of which the outer-periphery-surface radius is 1 mm larger, for example, at the pipe depth end than at the pipe inlet side is formed on the outer periphery of the body (1a) of the die (1). This mechanical expander is used to pipe-expand the pipe end portion and produce a seamless steel pipe. [EFFECTS] When steel pipes are joined to each other by circumferential welding at an installation site, excellent on-site welding characteristics are delivered. A seamless steel pipe excellent in pipe end size precision can be produced.

Description

Specification

Mechanical expander and method for producing seamless steel pipe

Technical field

[0001] The present invention relates to a mechanical expander for expanding a pipe end portion of a seamless steel pipe used in a pipeline for transporting fluids of oil and natural gas, and a seamless steel pipe using the mechanical expander. The present invention relates to a method of manufacturing a seamless steel pipe in which the pipe end portion is expanded.

Background art

[0002] When the pipeline is laid, connection (circumferential welding) between steel pipes for line pipes is performed at the laying site.

Therefore, the seamless steel pipe to be used is required to have welding characteristics such as weldability, that is, weld defects with high welding efficiency are unlikely to occur.

[0003] Therefore, high dimensional accuracy is required for the inner diameter of the welded portion. In addition, if a weld defect occurs, the weld is removed and welding is performed again. Therefore, the inner diameter of the pipe end part (with a pipe opening force of 100 mm in the longitudinal direction, preferably between 300 mm) is particularly high and dimensional. It is necessary to ensure accuracy.

[0004] By the way, it is difficult for a seamless steel pipe manufactured in a hot state to have a narrow tolerance with respect to an inner diameter dimensional accuracy that greatly affects welding workability compared to a welded steel pipe manufactured in a cold state. There is a case. Therefore, in particular, correction using a grinder or a cutting machine or correction by cold working is generally employed to ensure the inner diameter dimensional accuracy of the pipe end portion.

[0005] Further, Patent Document 1 discloses a method of correcting the inner diameter of the tube end portion by inserting a plug having a cylindrical body portion. Further, Patent Document 2 discloses that the material of the tube expansion die is changed to synthetic resin and the die segment is made elastic to expand the tube. Patent Document 1: Japanese Patent No. 2820043

Patent Document 2: Japanese Patent No. 2900819

Disclosure of the invention Problems to be solved by the invention

However, there is a concern that the strength at the connecting portion between the steel pipes may be reduced because the thickness of the pipe end portion is reduced by the correction by the grinder or the cutting machine. It is difficult to make a uniform correction in the longitudinal direction of the tube end force.

[0007] In addition, according to the techniques disclosed in Patent Document 1 and Patent Document 2, if the thickness of the tube end portion is reduced, the problem can be solved. The outer diameter of the die segment and the plug body is the same. Therefore, as will be described later, it is difficult to uniformly expand the tube end force in the longitudinal direction. In addition, in the case of Patent Document 1, in order to cope with various sizes, it is necessary to create a large number of plugs, which increases the manufacturing cost.

[0008] The problem to be solved by the present invention is that, in order to improve the accuracy of the inner diameter of a pipe end portion of a seamless steel pipe manufactured in the hot state, the conventional technique reduces the strength, It is difficult to uniformly expand the tube from the end to the long side.

Means for solving the problem

[0009] An object of the present invention is to improve the accuracy of the inner diameter of a pipe end portion of a seamless steel pipe manufactured hot.

For this purpose, the mechanical expander of the present invention inserts a cone and a die into the end of the tube to be expanded, and with the die fixed to the end of the tube, the cone is pulled out in the axial direction toward the outside of the tube. A mechanical expander that expands the end of the pipe by expanding the die outward in the radial direction by the action, and the outer periphery of the back end of the pipe is larger than the radius of the outer peripheral surface of the pipe mouth side on the outer periphery of the die The most important feature is the formation of a taper that increases the radius of the surface.

[0010] Further, the method for manufacturing a seamless steel pipe according to the present invention includes a die formed with a taper on the outer periphery of the body portion, in which the radius of the outer peripheral surface at the back end of the tube is larger than the radius of the outer peripheral surface on the tube port side. The main feature of the mecha-cal expander is to expand the tube end.

[0011] In the present invention, it is preferable that the taper value provided on the outer periphery of the body portion of the die is determined based on the experimental results of the inventors described later.

The invention's effect

[0012] According to the present invention, when connecting steel pipes by circumferential welding at a laying place, It is possible to produce seamless steel pipes with excellent pipe dimensional accuracy that exhibit excellent weldability characteristics.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the accompanying drawings along with the progress from the idea of the present invention to the solution of the problem.

[0014] As described above, in order to modify steel pipes of various sizes by expanding the pipe by plug insertion as disclosed in Patent Document 1, it is necessary to create a large number of plugs. Cost increases.

[0015] Therefore, the inventors examined the application of the mechanical expander that is used when manufacturing UOE steel pipes and that is expanded with a diameter-expandable pipe-expanding die only to the end part of the pipe.

As shown in FIG. 1, the mechanical expander includes a die 1 inserted into the inner surface of the steel pipe P to be expanded, and a cone 2 that pushes the die 1 to the inside force outward.

Of these, the die 1 is divided into a plurality of parts in the circumferential direction, the outer surface of the body la contacting the inner surface of the steel pipe P is parallel to the steel tube axis, and the inner surface contacting the outer surface of the cone 2 is the inner surface of the steel pipe P. The side to be inserted into the part has a tapered shape with a large diameter.

On the other hand, the outer surface of the cone 2 in contact with the die 1 has a taper shape with the same angle as the inner surface of the die 1, and the side to be inserted into the inner part of the steel pipe P has a large diameter.

[0019] A method of expanding the steel pipe P using such a mechanical expander is as follows.

First, the cone 2 is inserted into the end of the steel pipe P, and then the body la of the die 1 is inserted into the end of the steel pipe P.

[0020] Next, with the die 1 fixed to the steel pipe P, the cone 2 is pulled out in the axial direction toward the outside of the pipe. By pulling out the cone 2, the die 1 is pushed outward in the radial direction by the wedge action of both tapers provided on the cone 2 and the die 1.

[0021] Accordingly, since the amount of expansion of the steel pipe P by the die 1 can be controlled by controlling the drawing amount of the cone 2, the steel pipe P can be expanded to a plurality of inner diameters with one mechanical expander. it can. [0022] The inventors have expanded the diameter of only the pipe end portion of the seamless steel pipe by a method of expanding with a tube expansion die having a freely expandable diameter. As a result, although the inner diameter of the tube port could be controlled within a tolerance within a predetermined range, the inner diameter of the tube port was larger than the inner diameter of the inner part of the tube.

[0023] In order to obtain a uniform inner diameter in the tube axis direction, it is necessary to complete the processing with the working surface during pipe expansion (the outer peripheral surface of the body of the die contacting the inner surface of the steel tube) parallel to the tube axis. There is.

[0024] However, in the case of pipe expansion work with only the pipe end portion, the back end of the body la of the die 1 is restrained by the steel pipe P portion that is not expanded, so that The surface pressure acting on the die 1 is higher on the end side. Therefore, during pipe expansion, the amount of wear at the inner peripheral back end of the barrel la that contacts the cone 2 increases, and as a result, there is a gap with the cone 2 on the barrel la back end of the die 1. It becomes larger than the tube side of the trunk la (see Fig. 2 (a)).

In other words, the gap dl between the die 1 and the cone 2 at the back end side of the barrel la is larger than the gap d2 between the cone 2 and the cone 2 at the pipe opening, and simultaneously acts on the back end of the barrel la. Since the pressure is higher than the surface pressure acting on the tube opening, as shown in FIG. 2 (b), the die 1 is inclined with respect to the tube axis at the end of tube expansion processing. As a result, it was found that the inner diameter of the pipe mouth of the steel pipe P was larger than the inner diameter of the inner part of the pipe.

[0026] Incidentally, in the case of a UOE steel pipe, such a problem does not occur because the pipe is expanded over the entire length of the pipe end.

[0027] Based on the above knowledge, the inventors have made various studies on the shape of the die that completes the machining with the working surface parallel to the tube axis even when the die wear proceeds. An experiment was conducted.

Incidentally, an example of the experimental results conducted by the inventors is shown below.

[0028] The steel pipe used in the experiment is a steel pipe having an outer diameter of 323.9 mm and a wall thickness of 25.4 mm.

In this steel pipe, the axial length of the outer periphery of the body is 100 mm, and the outer periphery of the body is tapered to 0.5 mm, lmm, which is 0.5 mm larger than the outer periphery of the tube. A die with a difference in outer half diameter (0.5 mm and lmm) and a die without a taper were inserted, and these dice were expanded outwardly by pulling out the cone to expand the diameter. In addition, the inner peripheral surface of the inner part of the pipe of the die used was worn by 0.5 mm in the radial direction. [0029] After correcting the tube ends using the respective dies, the outer diameter and the wall thickness of the tube mouth portion and the axial back portion 100 mm away from the tube mouth portion in each correction portion are measured, and each inner diameter is measured. The inner diameter difference at the position in the axial direction at a distance of 100 mm from the tube opening and the tube opening was evaluated. The results are shown in Table 1 below.

[0030] [Table 1] Table 1

[0031] From Table 1, the value obtained by subtracting the outer radius difference of the die body due to the taper from the amount of wear of the die is approximately the die inner peripheral position of the pipe opening, and the pipe rocker is also located at the back in the axial direction. It was found that there was a difference in the inner radius of the steel pipe at the inner circumferential position separated by 100 mm.

[0032] Considering that the difference between the inner diameter of the pipe mouth and the inner diameter of the inner part of the pipe at the end of the steel pipe is 2mm or less (internal radius difference is 1mm or less), it is not a big problem in welding work. , The outer radius difference of the die body is lmm (If the body length is 100mm, the 2Z100 teno is used, so that the die wear amount force Omm is within the range of 2mm. The inner diameter difference of can be 1. Omm or less.

[0033] That is, when correcting only the tube end portion between 100 mm in the longitudinal direction and preferably 300 mm in the longitudinal direction, as shown in FIG. Use a die 1 that has a taper (2Z100 to 2Z300 taper) with a radius of 1mm larger on the outer peripheral surface of the tube at the end than the surface radius.

[0034] If a pipe end of a seamless steel pipe is expanded using such a mechanical expander having a die 1, the inner diameter of the pipe mouth becomes smaller by 1 mm than the inner diameter of the inner part of the pipe at the start of use of the die. . Therefore, even if the wear of the die progresses, the pipe end part and the pipe back part of the correction part The variation of the inner radius of the tool is smaller than that of the conventional tool, and as long as it is within the tolerance, pipe expansion can be performed, and the tool life due to wear can be greatly extended.

[0035] Further, considering that the difference between the inner diameter of the pipe mouth and the inner diameter of the inner part of the pipe at the end of the steel pipe is 2 mm or less (internal radius difference is 1 mm or less), it does not pose a major problem in welding construction Based on the above results, the outer radius difference of the die body is 0.5 to 1.5 mm (If the body length is 100 mm, the die wear force from Omm to 2. Omm can be reduced to 1Z100 to 3Z100. Within the range, the difference in the inner radius between the tube end and the tube back of the straightened part can be 1.5mm or less.

[0036] The present invention is not limited to the above-described example, and it is needless to say that the embodiment may be appropriately changed within the scope of the technical idea described in each claim.

Brief Description of Drawings

FIG. 1 is a schematic explanatory view of a mechanical expander, where (a) is a longitudinal sectional view of a main part, and (b) is an AA sectional view of FIG. (A).

[FIG. 2] (a) is a diagram for explaining a gap generated between a die and a cone, and (b) is a diagram showing a tilt of the die caused by wear on the back end side of the die at the moon.

FIG. 3 is a diagram illustrating a mechanical expander according to the present invention.

Explanation of symbols

[0038] P steel pipe

1 dice

la torso

2 cones

Claims

The scope of the claims

[1] Insert a cone and a die into the end of the tube to be expanded, and with the die fixed to the end of the tube, pull the cone out of the tube in the axial direction to remove the die radially outside by the wedge action. A mechanical expander that expands toward the end of the pipe and expands the end of the pipe, and the outer periphery of the pipe has a larger radius on the outer periphery of the die on the outer periphery of the pipe mouth A mechanical expander characterized in that it is formed.

[2] The pipe end is expanded with a mechanical expander having a die formed on the outer periphery of the barrel, with a taper that increases the radius of the outer peripheral surface of the back end of the tube compared to the radius of the outer peripheral surface on the tube mouth side. A method for producing a seamless steel pipe, characterized in that.